A cigarette manufacturing machine normally supplies a filter assembly machine with a stream of cigarette rods having a length twice as long as the finished cigarette. Each cigarette length is cut in half on the filter assembly machine, usually by means of rotary cutters. The halves are then separated to provide a gap sufficient to accommodate a double filter. The two cigarette halves and the double filter are then joined by means of two strips to form a double cigarette wherein the two cigarette halves are joined by the filter. The double filter is then cut in half, usually by means of rotary cutters, to produce a stream of single cigarettes which are then fed to the output of the filter assembly machine and fed to subsequent manufacturing machinery.
At the output of the filter assembly machine, sample cigarettes are usually withdrawn for inspection. The operating parameters of both the manufacturing and filter assembly machines are appropriately adjusted according to the outcome of the inspection.
Such inspection usually consists of inspecting the geometry of the cigarettes, in particular the length of the filter and relative cigarette portions, etc. Any discrepancy between the inspected cigarettes and set operating data is interpreted by the operators who then make appropriate adjustments, for example, of the manufacturing and filter assembly machine cutters, printing devices, etc. In this connection, it is important to bear in mind that correct interpretation of the inspection data depends on knowing the precise position of each individual cigarette subsequent to its being withdrawn from the manufacturing machine. For example, if the tobacco-filled portion is shorter than it should be, the position of the double cigarette lengths in relation to the cutters can only be corrected by trial and error if the precise position occupied beforehand by the sample cigarette in relation to the cutters is not known. In the case of double cigarette lengths produced on a standard manufacturing machine, each double cigarette is cut into two halves, one each to the right and left of the cutter, thus resulting in the formation of two distinct groups. For inspection data to be interpreted correctly, it is essential that one know to which group the sample cigarette belongs.
This is even more of a problem in the case of a dual rod cigarette manufacturing machine, which gives rise to no less than four distinct groups or types (two for each rod).